[once and for all] {adv. phr.} 1. One time and never […]

[once in a blue moon] {adv. phr.} Very rarely; very seldom; […]

[once in a while] {adv. phr.} Not often; not regularly; sometimes; […]

[once upon a time] {adv. phr.} Sometime before now, long ago. […]

[one of these days] or [some of these days] {adv. phr.} […]

[one's head off] {adv.} Loud or excessively. "I laughed my head […]

[or other] {adv.} - Used to emphasize indefinite words or phrases […]

[or so] {adv.} About; or a little more. * /Mr. Brown […]

[out back] {adv. phr.} In one's backyard. * /On the Fourth […]

[out cold] {adv.} or {adj.}, {informal} Unconscious; in a faint. * […]